<!doctype html>

<title>14 References - React From Zero</title>

<script src="https://unpkg.com/react@16.4.0/umd/react.development.js"></script>
<script src="https://unpkg.com/react-dom@16.4.0/umd/react-dom.development.js"></script>
<script src="https://unpkg.com/create-react-class@15.6.3/create-react-class.js"></script>
<script src="https://unpkg.com/@babel/standalone/babel.min.js"></script>

<div id="app"></div>

<script type="text/babel">
// Sometimes we need some state from an element or a component
// or it has to be directly modified somehow. For
// this case, we can tell React to create references.
var RefComponent = createReactClass({
  // First we tell React to render an input with a ref callback, it
  // will be called, when the DOM of the input element is available
  render: function() {
    return (
      <div>
        <input ref={this.handleRef} />
        <button onClick={this.handleClick}>Do Something</button>
      </div>
    );
  },

  // This callback is called when the input element was mounted into
  // the DOM and again, with null, when it was unmounted again
  // For elements the rendered DOM node will be stored
  // For components the instance of the component will be stored.
  handleRef(nameInput) {
    // We save a reference to it for later use.
    this.nameInput = nameInput;
  },

  // This callback is called when the button is clicked
  // and uses this.nameInput to read out the value of the input.
  handleClick: function() {
    console.log(this.nameInput.value);
  }
});

// Since references are local to their component
// they can be used as local IDs to get elements
// and don't override each other when another
// instance of the component is created
var reactElement = (
  <div>
    <RefComponent />
    <RefComponent />
    <RefComponent />
  </div>
);

ReactDOM.render(reactElement, document.getElementById("app"));
</script>